The present invention relates to detergent compositions containing as an essential ingredient a silicone suds controlling agent which is stable on storage. The concept of "stability" as used herein is in the context of protecting the silicone and preserving, maintaining or promoting its capability of suppressing or controlling the suds profile of a detergent surface active agent. More specificially, the invention in its broadest context encompasses detergent compositions comprising a detersive surfactant component and a silicone suds controlling agent which is separated or isolated within a protective matrix from the detersive surfactant.
In many industrial and household detergent operations involving aqueous solutions the formation of excessive suds is highly objectionable. Many prior art detergent compositions are high sudsing products. When such compositions are used in laundry washing machines, and especially in automatic dishwashers, they suds profusely and may cause the machines to overflow. Moreover, in horizontal tumbler-type washing machines, excess suds decrease the washing action by interfering with the free fall of the fabrics. A consequence may be that excessive suds or suds overflow may cause damage to the machine or may cause the user to compensate for excessive suds formation by using less detergent composition than is desirable to achieve good cleaning. On the other hand, users of detergent compositions for washing by hand, usually at lower temperatures, normally expect a certain amount of suds to be present at least until the detergent solution is so loaded with soil that it is no longer effective for cleaning. Thus, for some applications, such as automatic dishwashing, minimum suds formation is desirable; for so-called light-duty or fine fabric hand laundering a moderate suds level is useful; whereas a generous, but not excessive, suds blanket has come to be expected with so-called heavy-duty laundry compositions for washing heavily soiled fabrics. Adapting or controlling the suds profile of a detergent composition in these different applications has been a technical formulating challenge.
It is known that the sudsing of many prior art detergent compositions can be controlled by means of suds depressants such as long chain fatty acids, long chain fatty alcohols, esters and/or ethers thereof, or fatty acid amines and amides. Many of these suds depressants appear to have an adverse effect upon the whiteness maintenance properties of the detergent compositions and most are only useful and effective at lower temperatures. Moreover, many of such prior art materials are sensitive to water hardness; some cannot be used because of their interaction with washing additives; and some interact adversely with the soil or are ineffective under alkaline conditions.
Silicones are widely known and taught for use as highly effective suds controlling agents. For example, U.S. Pat. No. 3,455,839 relates to compositions and processes for defoaming aqueous solutions by incorporating therein small amounts of polydimethylsiloxane fluids.
Useful suds controlling silicones are mixtures of silicone and silanated silica as described, for instance, in German Pat. Application DOS 2,124,526.
Additionally, German Pat. No. 2,232,262 relates to silicone suds controlling agents comprising sodium tripolyphosphate surface-coated with an organopolysiloxane.
Although silicone defoamers and suds controlling agents have been known for many years, such materials have not heretofore been successfully incorporated into a detergent composition. Rather, the silicones are characteristically used once the detergent composition has already been added to the aqueous cleaning bath. This, of course, is not desirable, nor always feasible, since the user is not predisposed to add such materials separately to a fabric laundering bath or automatic dishwasher. Accordingly, it would be desirable to provide detergent compositions containing a stable silicone suds controlling agent as an integral ingredient.
A variety of means have been suggested for employing silicones in combination with detergent compositions. For example, it would be expected that such material could simply be sprayed onto, or otherwise admixed, with a detergent composition to provide the desired suds control. However, simple admixture of a silicone with a detergent composition has been shown experimentally not to be a satisfactory means for providing the suds controlling function. While such silicone-containing compositions initially exhibit a controlled suds, the suds control property of the silicone is very significantly reduced or perhaps even completely lost during storage of the composition for even relatively short periods. For this reason, attempts have been made to stabilize or protect the silicones in the detergent compositions, for example by sorption on a carrier material (see German Pat. No. 2,232,262, above). However, experiments have shown that adsorbing a silicone on a porous carrier does not provide detergent compositions having a substantial foam controlling action after storage.
It has now been found that the problem with formulating stable, controlled sudsing detergent compositions containing silicones arises from an interaction between the detersive surfactant (i.e., detergent) component of such mixtures and the silicone suds controlling agent. While the exact mechanism is not known, it appears that, on storage, the surfactant component interacts with the silicone to render it water-dispersible. On admixture of the detergent composition with water, the silicone is dispersed throughout the aqueous liquor rather than migrating to the air/water interface. Accordingly, the silicone cannot perform its desired suds controlling function.
Having recognized the problem of the heretofore unsuspected interaction of the detergent material with the silicone on storage, it has now been found that by isolating the silicone material from said detergent, compositions having controlled suds patterns even after prolonged storage can be provided.
Accordingly, it is an object of this invention to provide detergent compositions having a controlled suds pattern. (By "controlled suds pattern" herein is meant a suds height which is substantially zero in an automatic dishwashing composition, and which is low-to-medium in height over a broad temperature range in the case of hand- and machine-laundering products.)
It is further object herein to provide compositions and processes for incorporating silicone suds controlling agents in detergent compositions such that effective suds control is obtained even after prolonged storage.
These and other objects are obtained herein, as will be seen from the following disclosure.